Chemical tests are a central part of every DUI / DWI investigation. However, a chemical test result that indicates a driver was over the legal limit doesn’t necessarily mean an automatic conviction.  Chemical tests are typically a central part of prosecutors’ cases, but they can also be very helpful to the defense. There are many challenges can be made to blood, breath and urine tests in DUI / DWI cases.

The DUI / DWI defense attorneys from www.NotDrunk.com are well-versed in the various attacks on chemical tests. Drivers accused of DUI / DWI typically must submit to a chemical test of blood, breath, or urine. In some states, motorists accused of driving under the influence are allowed to choose between a breath or blood test. In other states, the driver must submit to whatever test is given.

Blood or urine tests are given when motorists are accused of driving under the influence of drugs.  Generally, there is no right to a urine test in DUI / DWI cases involving only alcohol.  Urine testing in drinking and driving cases has been deemed too unreliable to withstand courtroom challenges.

DUI / DWI arrests often result in two separate charges or a single charge broken down into two or more elements – driving under the influence, and violation of the state’s “per se” laws.

A driving under the influence allegation focuses on whether the driver was so impaired by alcohol or drugs that he or she was unable to operate a vehicle safely. Per se allegations focus solely on whether the driver’s  blood or breath alcohol content (BAC) was.08 percent or greater – now the legal limit in all 50 states.

Chemical tests of the driver’s blood, breath or urine to determine BAC are obviously fundamental to any prosecutor’s per se case.  However, chemical tests are also central to the allegation of driving under the influence, because many forensic alcohol experts believe that all individuals are impaired if they have a certain BAC. Some believe that level to be .10 percent, some .08 percent, and the most conservative will assert that all people are under the influence at .05 percent BAC. 

Chemical testing is so much a part of every drunk driving case that both courts and motor vehicle departments in many states can impose strict sanctions on drivers who refuse to submit to a chemical test following a DUI / DWI arrest.

However, while chemical testing may accurately determine BAC at the time of testing, it is much more difficult to pinpoint the motorist’s BAC at the time of driving.  Remember, it’s not against the law to exceed the legal limit at the police station hours after being behind the wheel – the offense is driving while intoxicated, not having a BAC above the legal limit at a later time.  Alcohol levels change over time, so this point is critical to successful DUI / DWI defense.

Chemical tests aren’t always accurate – not even close. There are many proven challenges available to attack blood and breath tests in driving under the influence cases.  Drug tests are even more unreliable, and therefore more open to challenge. Drug tests identify metabolites in the blood or urine, not the drug itself.  Also, because of the amount of time that many drugs stay in the system, it is incredibly difficult to demonstrate that a person was impaired at the time of driving.